Single-layer flexible silicone graphene composite anticorrosive paint and preparation method thereof

Abstract

The present application relates to the technical field of metal anticorrosive coating, and discloses a single-layer flexible organic silicon graphene composite anticorrosive coating and a preparation method thereof, wherein the coating is formed by mixing component A and component B at a mass ratio of 1:(0.8-1.2); component A comprises flexible organic silicon resin, epoxy-silane modified graphene paste, nano-silicon dioxide, organic silicon toughening agent and additives; and component B comprises polyurethane curing agent and adhesion promoter. The epoxy-silane modified graphene paste is prepared by using a high-pressure hydrothermal method, and the inorganic filler is dispersed in the flexible resin matrix by using a step-by-step variable shear process. The coating system solves the problems of large brittleness and easy cracking of thick coating of traditional organic silicon coating by constructing a rigid-flexible crosslinking network, realizes single-layer thick film coating, and has excellent adhesion, flexibility and long-term salt fog corrosion resistance, so that the construction process can be simplified and the comprehensive protection effect of metal facilities can be improved.

Description

Technical Field

[0001] This invention relates to the field of metal anti-corrosion coating technology, specifically to a single-layer flexible organosilicon graphene composite anti-corrosion coating and its preparation method. Background Technology

[0002] Currently, in industrial sectors such as power facilities, chemical equipment, and marine engineering, the economic losses and safety hazards caused by metal corrosion are becoming increasingly severe. Applying high-performance heavy-duty anti-corrosion coatings is a primary means of extending the service life of steel structures and ensuring the safe operation of equipment. As industry demands for environmental standards and construction efficiency continue to rise, the research and development direction of anti-corrosion coatings is gradually shifting towards long-lasting durability, integrated functionality, and simplified construction processes, aiming to reduce maintenance costs throughout the entire lifecycle.

[0003] For the aforementioned application scenarios, existing high-temperature and weather-resistant anti-corrosion coatings often use silicone resins as the main film-forming material. They leverage the high-bond-energy silicon-oxygen bond structure in the main molecular chain to provide thermal stability and weather resistance, and attempt to introduce two-dimensional nanomaterials such as graphene to enhance the coating's physical barrier against corrosive media. In the preparation of these coatings, a physical blending process is typically used to mix and disperse the resin matrix, curing agent, and various functional fillers. After the coating is applied to the surface of the metal substrate, it mainly cures into a film through the cross-linking reaction of the resin functional groups or solvent evaporation. The labyrinth effect formed by the fillers within the coating blocks the penetration of water vapor, oxygen, and chloride ions.

[0004] However, existing technologies still face many limitations in practical applications. Traditional silicone coatings typically have excessively high cross-linking density after curing, resulting in high hardness but insufficient toughness. The internal stress generated by curing shrinkage is difficult to release effectively, and microcracks easily form as the coating thickness increases, making it difficult to achieve the integrity of a single thick-film coating. On the other hand, unmodified graphene has high surface energy and poor interfacial compatibility with organic resin matrices. Simple physical stirring is insufficient to achieve ideal dispersion, leading to agglomeration in the coating system. This not only fails to build a dense barrier network but also creates corrosion channels due to weak interfacial bonding. Furthermore, to balance adhesion to the substrate and surface weather resistance, existing protective systems often rely on a complex coating process of primer, intermediate coat, and topcoat, with long interlayer intervals, failing to meet the urgent needs for construction efficiency in high-altitude operations or rapid maintenance.

[0005] Therefore, the present invention provides a single-layer flexible organosilicon graphene composite anti-corrosion coating and its preparation method to overcome the shortcomings of the prior art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a single-layer flexible organosilicon-graphene composite anti-corrosion coating and its preparation method. This solves the problems that existing organosilicon anti-corrosion coatings generally suffer from excessively high crosslinking density after curing, leading to high coating brittleness and easy cracking when thick coatings are applied. Furthermore, ordinary graphene fillers are difficult to disperse and tend to agglomerate in organic resins, making it impossible to provide long-term anti-corrosion performance in single-layer coating systems.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a single-layer flexible organosilicon-graphene composite anti-corrosion coating, which adopts the following technical solution:

[0009] A single-layer flexible organosilicon graphene composite anti-corrosion coating is composed of component A and component B, with a mass mixing ratio of component A to component B of 1:(0.8-1.2).

[0010] Component A contains the following raw materials in parts by weight: 30-50 parts flexible silicone resin; 5-15 parts epoxy silane modified graphene slurry; 2-5 parts nano silica; 3-8 parts silicone toughening agent; 0.2-1 part defoamer; 0.5-2 parts leveling agent; and 0.1-0.5 parts catalyst.

[0011] Component B contains the following raw materials in parts by weight: 20-40 parts of polyurethane curing agent; 1-3 parts of adhesion promoter.

[0012] The advantages of the above technical solution are as follows: This invention utilizes flexible silicone resin and polyurethane curing agent to construct a tough organic-inorganic hybrid cross-linked network. Specifically, during the film formation process of this coating system, the flexible segments introduced by the flexible silicone resin can effectively reduce the internal stress generated by curing shrinkage, giving the coating mechanical properties to resist cracking in a thick film state; at the same time, the epoxy-containing silane-modified graphene slurry, as the core anti-corrosion component, utilizes its surface organic functional groups to chemically bond with the resin matrix, solving the problem of poor interfacial compatibility between inorganic fillers and organic matrix. The uniformly dispersed graphene sheets form a dense physical barrier layer inside the coating, extending the path for water, oxygen, and corrosive media to penetrate to the substrate surface, thereby achieving long-term anti-corrosion under single-coat conditions.

[0013] Preferably, the flexible silicone resin is an epoxy-terminated silicone oil modified resin; and the silicone toughening agent is a polyether-modified silicone oil.

[0014] The advantages of the above technical solution are as follows: While retaining the high-temperature resistance and weather resistance of organosilicon, the epoxy groups at the ends of the silicone oil-modified resin react with the curing agent, reducing the rigidity of the crosslinking points. The polyether-modified silicone oil, acting as a toughening agent, further generates an internal plasticizing effect through the flexibility of the polyether segments, synergistically improving the impact resistance and flexural flexibility of the coating, ensuring that the coating does not undergo brittle cracking under alternating hot and cold temperatures or external impact.

[0015] Preferably, the NCO group content in the polyurethane curing agent is ≥12% by mass; the adhesion promoter is a silane coupling agent; and the particle size of the nano silica is 10-50 nm.

[0016] Preferably, the catalyst is an organotin catalyst; the defoamer is a mineral oil defoamer; and the leveling agent is a polyether-modified organosilicon leveling agent.

[0017] The advantages of the above technical solution are: the high NCO content polyurethane curing agent ensures that the system has sufficient active groups to fully crosslink with the active sites on the resin and modified graphene surface, forming a dense three-dimensional network structure. Nano-silica particles fill the gaps between polymer chain segments, providing physical reinforcement and strengthening, and, in conjunction with silane adhesion promoters, enhance the coating's anchoring force to the metal substrate.

[0018] Preferably, the epoxy-containing silane-modified graphene slurry is prepared by hydrothermal grafting and reduction of graphene oxide with an epoxy-containing silane coupling agent, and then dispersion. The solid content of the epoxy-containing silane-modified graphene slurry is (5-15) wt%.

[0019] The advantage of the above technical solution lies in the fact that the component is not a simple physical mixture of graphene and resin, but a chemically grafted functional filler. Utilizing a high-pressure hydrothermal environment, the epoxy-containing silane coupling agent undergoes hydrolysis and condensation reaction with the hydroxyl and carboxyl groups on the surface of graphene oxide, firmly grafting organosilicon and epoxy functional groups onto the graphene sheet surface. The subsequent reduction step removes excess epoxy groups, restoring the conjugated structure and conductivity of graphene while retaining the grafted active sites. This modification allows graphene to participate in the chemical cross-linking reaction during subsequent mixing and curing with components A and B, transforming physical doping into chemical bonding and eliminating interfacial defects.

[0020] Secondly, the present invention provides a method for preparing a single-layer flexible organosilicon-graphene composite anti-corrosion coating, employing the following technical solution:

[0021] A method for preparing a single-layer flexible organosilicon-graphene composite anti-corrosion coating, used to prepare the aforementioned coating, includes the following steps:

[0022] S1. Preparation of epoxy-containing silane-modified graphene slurry: Graphene oxide and silane coupling agent are mixed in a solvent and subjected to hydrothermal reaction under closed high pressure. After the reaction is completed, the slurry is obtained by reduction, washing and redispersing.

[0023] S2. Preparation of component A: Flexible organosilicon resin, nano-silica and organosilicon toughening agent are mixed and dispersed at high speed, then epoxy-silane modified graphene slurry is added and dispersed at low speed, and finally leveling agent, defoamer and catalyst are added and stirred evenly.

[0024] S3. Preparation of Component B: Mix and filter the polyurethane curing agent and adhesion promoter;

[0025] S4. Mixing: Mix component A and component B in the specified proportions and allow them to mature before use.

[0026] The advantage of the above technical solution lies in the fact that, under closed, high-pressure, and specific temperature conditions, the solvent is in a subcritical state, possessing a high diffusion coefficient and a low dielectric constant. This enhances the penetration ability and reactivity of the silane coupling agent between graphene oxide layers. The specific reaction process is as follows: First, the silane coupling agent hydrolyzes in a hydrothermal environment to generate silanol; second, the silanol groups undergo dehydration condensation with the hydroxyl groups on the graphene oxide surface to form stable Si-OC covalent bonds; finally, the graphene structure is repaired through a reduction reaction. This process achieves high-density and uniform grafting of organic functional groups onto the graphene surface.

[0027] The process first employs high-speed dispersion (high shear force) to treat the resin and nano-silica, aiming to break up the nanoparticle aggregates and ensure the uniform distribution of the inorganic reinforcing phase. Subsequently, after adding epoxy-based silane-modified graphene slurry, the dispersion rate switches to low-speed dispersion (low shear force). This design is to avoid the high-intensity mechanical shearing damaging the two-dimensional sheet structure and aspect ratio of graphene. Maintaining the intact large-sheet structure of graphene is crucial for forming the labyrinth effect and blocking the diffusion of corrosive media.

[0028] Preferably, in step S1, the mass ratio of graphene oxide to silane coupling agent is 1:(0.3-0.7); the hydrothermal reaction temperature is 120-150℃, and the reaction time is 4-8 hours.

[0029] The advantage of the above technical solution is that the defined mass ratio and reaction parameters ensure that the grafting rate is within the optimal range. If the grafting rate is too low, the improvement in dispersibility is not significant; if the grafting rate is too high, the excessively thick silane layer will affect the stacking density of the graphene sheets.

[0030] Preferably, in step S1, the silane coupling agent is γ-glycidoxypropyltrimethoxysilane (KH-560); and the graphene oxide sheet diameter is ≤3μm.

[0031] The advantages of the above technical solution are as follows: γ-glycidyl etheroxypropyltrimethoxysilane is selected because the epoxy groups carried in its molecular structure have excellent chemical compatibility with the flexible organosilicon resin and polyurethane curing agent in this system, which can ensure that graphene is not only a physical filler, but also participates in curing and cross-linking as an active node, thereby improving the interfacial bonding force; the graphene oxide sheet diameter is strictly controlled to be ≤3μm, which aims to balance the barrier and dispersibility of the filler. Sheets within this size range can ensure sufficient aspect ratio to maintain the labyrinth effect, and can effectively reduce the risk of sedimentation or surface defects caused by agglomeration of large sheets during coating storage and construction, thus ensuring the surface smoothness and density of the thick film coating.

[0032] Preferably, in step S2, the high-speed dispersion speed is 1000-1500 rpm and the time is 15-25 minutes; the low-speed dispersion speed is 400-600 rpm and the time is 20-40 minutes.

[0033] The advantage of the above technical solution is that the precisely controlled shear rate and time parameters balance the contradiction between dispersion efficiency and material structure protection, ensuring that the final coating system has both excellent storage stability and anti-corrosion performance after film formation.

[0034] Preferably, the process also includes the following steps: applying the mixed and matured coating to the surface of the metal substrate, and controlling the dry film thickness of a single layer of coating to be 110-130μm.

[0035] The advantage of adopting the above technical solution is that it clarifies the application method of the coating. Thanks to the rigid-flexible cross-linked network design in the formulation of this invention, the coating can withstand the curing stress of a single-layer thick film exceeding 100 micrometers without generating microcracks, overcoming the drawback of traditional anti-corrosion coatings requiring multiple coats to achieve the specified thickness, and improving construction efficiency.

[0036] This invention provides a single-layer flexible organosilicon-graphene composite anti-corrosion coating and its preparation method. It has the following beneficial effects:

[0037] 1. This invention utilizes a high-pressure hydrothermal reaction process to graft terminal epoxy-based silanes onto the surface of graphene, achieving chemical bonding between the inorganic filler and the organic resin matrix. This chemical modification improves the wettability and dispersion stability of graphene in the resin system, effectively avoiding the agglomeration problem that easily occurs in traditional physical mixing methods. The uniformly dispersed graphene sheets, tightly bonded to the matrix, construct a dense physical barrier network within the coating, extending the diffusion path of corrosive media such as water molecules, chloride ions, and oxygen to the surface of the metal substrate, thereby enhancing the coating's salt spray resistance and long-term corrosion protection.

[0038] 2. This invention utilizes epoxy-terminated silicone oil-modified resin in combination with polyurethane curing agents and silicone toughening agents to construct a rigid-flexible interpenetrating polymer network structure. The flexible segments introduced into this system can effectively absorb and dissipate the shrinkage stress generated during the curing process of the coating, as well as the thermal stress generated under alternating hot and cold environments, overcoming the technical defects of traditional silicone anticorrosive coatings, which are high in hardness but brittle and prone to cracking when applied in thick coats. This allows the coating to achieve a dry film thickness of 110-130 micrometers with a single coat while maintaining excellent adhesion, flexibility, and thermal shock resistance.

[0039] 3. This invention employs a stepwise variable shearing preparation process. By first dispersing nano-silica at high speed and then dispersing the epoxy-containing silane-modified graphene slurry at low speed, the dispersion state of each component is optimized. This process ensures the uniform distribution of nanoparticles in the resin for reinforcement while maximizing the preservation of the complete two-dimensional sheet structure and high aspect ratio of graphene, preventing sheet breakage due to excessive mechanical shearing force. The complete graphene sheet structure can fully exert its physical shielding effectiveness, synergistically improving the mechanical strength and dielectric barrier efficiency of the final cured coating. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Preparation Examples 1-3:

[0042] Preparation Example 1:

[0043] This preparation example provides a method for preparing epoxy-silane-modified graphene slurry A. The specific steps are as follows: First, a certain amount of graphene oxide (sheet diameter ≤ 3 μm) and silane coupling agent KH-560 are weighed, with the mass ratio controlled at 1:0.3. The above raw materials are added to an appropriate amount of ethanol / water mixed solvent and ultrasonically dispersed to obtain a mixed dispersion. Subsequently, the mixed dispersion is transferred to a high-pressure reactor and sealed. The reaction temperature is set at 120℃, and a hydrothermal reaction is carried out under stirring conditions for 4 hours to allow the terminal epoxy-silanes to be fully grafted onto the graphene surface. After the reaction, the product is reduced and washed with ethanol by centrifugation to remove unreacted residues. Finally, the washed precipitate is redispersed in a dispersion medium, and the solid content is adjusted to 5 wt% to obtain epoxy-silane-modified graphene slurry A.

[0044] Preparation Example 2:

[0045] This preparation example provides a method for preparing epoxy-silane-modified graphene slurry B. The specific steps are as follows: Graphene oxide and silane coupling agent KH-560 are weighed and mixed at a mass ratio of 1:0.5. The mixture is added to a mixed solvent system of ethanol and water, and after high-speed stirring and ultrasonic-assisted dispersion, it is transferred to a high-pressure reactor equipped with a polytetrafluoroethylene liner. The reactor is heated to 135°C and maintained at this temperature for 6 hours for a high-temperature hydrothermal grafting reaction. After the reaction is completed and cooled to room temperature, the reaction product is subjected to a reduction process. Subsequently, the product is washed and filtered multiple times with deionized water and anhydrous ethanol alternately until the filtrate is neutral. The filter cake is collected and a solvent is added for high-speed dispersion, finally obtaining epoxy-silane-modified graphene slurry B with a solid content of 10 wt%.

[0046] Preparation Example 3:

[0047] This preparation example provides a method for preparing epoxy-containing silane-modified graphene slurry C. The specific steps are as follows: Graphene oxide and silane coupling agent KH-560 are accurately weighed at a mass ratio of 1:0.7. The weighed raw materials are added to an ethanol / water mixed solvent, mixed evenly, and then placed in a high-pressure reaction device. The temperature of the reaction system is set to 150℃, and a hydrothermal reaction is carried out for up to 8 hours under continuous stirring to achieve deep grafting and modification of organosilicon functional groups between graphene layers. After the reaction is completed, the temperature of the reaction system is lowered to 95℃, and hydrazine hydrate solution (mass fraction of 80%) is added as a reducing agent, wherein the mass ratio of hydrazine hydrate to the added graphene oxide is 2:1. The reaction is stirred at a constant temperature for 4 hours to remove oxygen-containing groups and restore the conjugated structure. Subsequently, the solid phase is separated by centrifugation. The solid phase is repeatedly washed to remove impurities, and finally dispersed in a liquid medium. The solid content of the slurry is precisely adjusted to 15wt%, thus obtaining epoxy-containing silane-modified graphene slurry C.

[0048] Examples 1-3:

[0049] Example 1:

[0050] This embodiment provides a single-layer flexible organosilicon graphene composite anti-corrosion coating and its preparation method. The coating is composed of component A (main agent) and component B (curing agent).

[0051] Component A comprises the following raw materials in parts by weight: 30 parts of flexible organosilicon resin, 5 parts of epoxy-containing silane modified graphene slurry A (obtained from Preparation Example 1), 2 parts of nano-silica, 3 parts of organosilicon toughening agent, 0.2 parts of defoamer, 0.5 parts of leveling agent, and 0.1 parts of catalyst.

[0052] Component B comprises the following raw materials in parts by weight: 20 parts polyurethane curing agent and 1 part adhesion promoter.

[0053] The preparation and application method of this coating includes the following steps:

[0054] S1: Preparation of the main agent. First, weighed flexible silicone resin, nano-silica, and silicone toughening agent are added to a high-speed disperser. The speed is set to 1000 rpm, and high-speed dispersion is carried out for 15 minutes to initially disperse the inorganic nanoparticles in the resin matrix. Then, epoxy-silane modified graphene slurry A is added, and the speed is adjusted to 400 rpm. Dispersion is continued for 20 minutes to ensure that the graphene sheets are uniformly distributed and not damaged under low shear force. Finally, leveling agent, defoamer, and catalyst are added in sequence, stirred at low speed until uniform, filtered, and packaged to obtain component A.

[0055] S2: Curing agent preparation. The polyurethane curing agent and adhesion promoter are mixed in the above-mentioned weight ratio, and after filtration to remove impurities, component B is obtained.

[0056] S3: Mixed coating. Before application, mix component A and component B at a mass ratio of 1:0.8, stir evenly, and allow to mature for a certain period of time before spraying.

[0057] Example 2:

[0058] This embodiment provides a single-layer flexible organosilicon graphene composite anti-corrosion coating and its preparation method. The coating is composed of component A (main agent) and component B (curing agent).

[0059] Component A comprises the following raw materials in parts by weight: 40 parts of flexible organosilicon resin, 10 parts of epoxy-containing silane modified graphene slurry B (obtained from Preparation Example 2), 3.5 parts of nano-silica, 5.5 parts of organosilicon toughening agent, 0.6 parts of defoamer, 1.2 parts of leveling agent, and 0.3 parts of catalyst.

[0060] Component B comprises the following raw materials in parts by weight: 30 parts polyurethane curing agent and 2 parts adhesion promoter.

[0061] The preparation and application method of this coating includes the following steps:

[0062] S1: Preparation of the main agent. Flexible organosilicon resin, nano-silica, and organosilicon toughening agent were added to a high-speed disperser, and the speed was adjusted to 1250 rpm for 20 minutes. Then, epoxy-silane-modified graphene slurry B was added, and the speed of the equipment was adjusted to 500 rpm for 30 minutes of continuous dispersion. Stable dispersion was achieved by utilizing the interfacial interaction between silane-modified graphene and modified resin. Finally, leveling agent, defoamer, and catalyst were added, and the mixture was stirred at low speed until homogeneous to obtain component A.

[0063] S2: Curing agent preparation. Weigh the polyurethane curing agent and adhesion promoter according to the formula, mix them evenly and filter to obtain component B.

[0064] S3: Mixed coating. During application, mix component A and component B at a precise mass ratio of 1:1.0, mechanically stir until homogeneous, and apply the coating after the air bubbles have dissipated and the mixture has matured.

[0065] Example 3:

[0066] This embodiment provides a single-layer flexible organosilicon graphene composite anti-corrosion coating and its preparation method. The coating is composed of component A (main agent) and component B (curing agent).

[0067] Component A comprises the following raw materials in parts by weight: 50 parts of flexible organosilicon resin, 15 parts of epoxy silane modified graphene slurry C (obtained from Preparation Example 3), 5 parts of nano-silica, 8 parts of organosilicon toughening agent, 1 part of defoamer, 2 parts of leveling agent, and 0.5 parts of catalyst.

[0068] Component B comprises the following raw materials in parts by weight: 40 parts polyurethane curing agent and 3 parts adhesion promoter.

[0069] The preparation and application method of this coating includes the following steps:

[0070] S1: Preparation of the main agent. Flexible organosilicon resin, nano-silica, and organosilicon toughening agent were mixed and placed in a dispersion device and dispersed at a high speed of 1500 rpm for 25 minutes to ensure that the filler was fully deagglomerated; then, a high concentration of epoxy-containing silane-modified graphene slurry C was added, the speed was reduced to 600 rpm, and dispersion was continued for 40 minutes to allow the high-content graphene to build a dense physical shielding network in the resin system; finally, leveling agent, defoamer, and catalyst were added, and after stirring evenly, component A was obtained.

[0071] S2: Curing agent preparation. Mix sufficient polyurethane curing agent with adhesion promoter, and obtain component B through filtration.

[0072] S3: Mixed coating. Before use, mix component A and component B at a mass ratio of 1:1.2, stir thoroughly to ensure the cross-linking and curing reaction is fully carried out, and it can be used after curing.

[0073] Comparative Examples 1-4:

[0074] Comparative Example 1:

[0075] Compared with Example 2, the difference is that the epoxy-containing silane-modified graphene slurry B used in component A is replaced with an equal amount of physical mixture of un-hydrothermally grafted graphene oxide and silane coupling agent KH-560. The other raw material components, dosage ratios and preparation processes are the same as in Example 2.

[0076] Comparative Example 2:

[0077] Compared with Example 2, the difference is that: no epoxy silane-modified graphene slurry B is added to component A, and the missing weight parts (10 parts) are made up by flexible organosilicon resin. The other raw material components, dosage ratios and preparation processes are the same as in Example 2.

[0078] Comparative Example 3:

[0079] Compared with Example 2, the difference is that no organosilicon toughening agent is added to component A, and the flexible organosilicon resin (terminated epoxy silicone oil modified resin) is replaced with an equal amount of ordinary methylphenyl silicone resin. The remaining raw material components, dosage ratios and preparation processes are the same as in Example 2.

[0080] Comparative Example 4:

[0081] Compared with Example 2, the difference is that in the S3 mixing step, the mixing mass ratio of component A to component B is adjusted to 1:0.5, while the other raw material components, dosage ratios, and independent preparation processes of components A and B are the same as in Example 2.

[0082] Test Example 1-2:

[0083] Test Example 1: Feasibility Verification of the Technical Solution of the Invention

[0084] Experimental Description: This test case aims to verify the comprehensive performance of Examples 1-3 under different formulation concentrations and process parameters.

[0085] Substrate treatment: Q235 steel plate (150mm×70mm×1mm) is selected and surface treatment is carried out by sandblasting process. The rust removal grade reaches Sa2.5 and the surface roughness Rz is controlled at 40-70μm.

[0086] Coating Application: Take Component A and Component B prepared in Examples 1, 2, and 3 respectively, and mix them according to their respective set mass ratios. After mechanically stirring until homogeneous, allow the mixture to stand for 20 minutes to eliminate air bubbles. Use a high-pressure airless sprayer to spray the coating onto the steel plate surface, forming a film in one pass, controlling the dry film thickness to be 120±10μm.

[0087] Curing conditions: The coated sample was placed in an environment with a temperature of 25±2℃ and a relative humidity of 50±5% for 7 days. The test was conducted after the coating was fully cured.

[0088] Testing standards:

[0089] Adhesion: GB / T 9286-2021 "Paints and Varnishes - Cross-cut Test";

[0090] Neutral salt spray resistance: GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test";

[0091] High temperature resistance: GB / T 1735-2009 Determination of heat resistance of paints and varnishes, observed after being kept at 250℃ for 48 hours;

[0092] Flexibility: GB / T 1731-2020 "Determination of Flexibility of Paint Film and Putty Film";

[0093] Impact resistance: GB / T 1732-2020 "Test Method for Impact Resistance of Coating Film".

[0094] Test data: The performance test data of Examples 1-3 are recorded in the table below.

[0095] Table 1. Test data of the physical and chemical properties of the coatings in Examples 1-3

[0096] Conclusions and Mechanism Analysis: Based on the data in Table 1, Examples 1-3 all exhibited excellent and stable comprehensive performance, verifying the feasibility of the formulation system of this invention.

[0097] Mechanism of long-lasting corrosion resistance: The salt spray resistance time of all three sets of data exceeded 5800 hours, with Example 2 reaching 6216 hours. This indicates that grafting organosilicon functional groups via high-pressure hydrothermal reaction improves the wettability and dispersibility of graphene in the resin matrix. The uniformly dispersed graphene sheets construct a dense physical barrier network within the coating, effectively extending the path length for corrosive media (water, oxygen, chloride ions) to penetrate to the substrate surface.

[0098] Mechanism of Flexibility and Temperature Resistance: Silicone coatings typically have high hardness but are also brittle. In this test, the coating did not crack after being subjected to 250℃, and its flexibility reached 1mm at room temperature, with an impact resistance of 50kg·cm. This confirms that the interpenetrating network structure formed by the flexible silicone resin (epoxy-terminated silicone oil modified resin) and the polyurethane curing agent, combined with the plasticizing effect of the silicone toughening agent, effectively dissipates the internal stress generated by coating curing shrinkage and thermal expansion and contraction, solving the technical problem of easy cracking in single-layer thick coatings.

[0099] Test Example 2: Comparative Analysis of the Effects of Key Components and Their Proportions

[0100] Experimental description:

[0101] This test example selects Example 2, which has the best performance in Test Example 1, as the reference group. It is compared with Comparative Example 1 (graphene physical mixing without modification), Comparative Example 2 (without graphene), Comparative Example 3 (without flexible toughening system), and Comparative Example 4 (curing agent ratio imbalance) under the same conditions to verify the key role of each technical feature.

[0102] Experimental control: The sample preparation, substrate treatment, coating thickness (120±10μm) and curing conditions of each comparative example were strictly consistent with those of Test Example 1 to ensure the parallel comparability of the data.

[0103] Test items: The main focus is on adhesion, salt spray resistance, high temperature resistance, flexibility, and impact resistance.

[0104] Test data: The performance comparison test results of each group of samples are recorded in the table below.

[0105] Table 2. Performance difference comparison data between Example 2 and Comparative Examples 1-4

[0106]

[0107] Conclusions and Mechanism Analysis: By comparing the data in Table 2, the following technical conclusions are drawn:

[0108] The criticality of interfacial chemical bonding (Comparative Example 2 vs. Comparative Example 1):

[0109] Comparative Example 1 introduced graphene using a physical mixing method, resulting in a decrease in salt spray resistance life from 6216 hours to 3528 hours and a reduction in adhesion.

[0110] Analysis: Unmodified graphene has high surface energy and poor interfacial compatibility with organic resins, making it prone to agglomeration. These agglomerates not only fail to form an effective shielding layer but also become defects within the coating. This invention utilizes a high-pressure hydrothermal reaction to graft terminal epoxy silanes onto the graphene surface, achieving chemical bonding between the filler and the resin, thereby improving the coating's density and corrosion resistance.

[0111] The core role of physical barriers (Comparative Example 2 and Comparative Example 2):

[0112] Comparative Example 2, which does not contain graphene, has a salt spray resistance of only 1800 hours.

[0113] Analysis: The data directly confirms that in a single-layer system that does not rely on zinc-rich primer cathodic protection, the physical barrier effect brought about by the high aspect ratio of graphene sheets is the core mechanism for blocking the vertical penetration of corrosive media.

[0114] Regulation of thermomechanical properties by flexible toughening systems (Comparative Example 2 and Comparative Example 3):

[0115] Comparative Example 3 used ordinary silicone resin without toughening agent. Its high temperature resistance test showed cracks, its impact resistance was only 15 kg·cm, and its flexibility was extremely poor (>10 mm cracking).

[0116] Analysis: Ordinary silicone resins have high crosslinking density and strong rigidity, making them unsuitable for the internal stress of thick-film coatings. This invention introduces flexible segments (terminated epoxy-based silicone oil-modified resin) and elastomer components (polyurethane curing agent, toughening agent) to construct a crosslinking network that combines rigidity and flexibility. This structure can effectively absorb and dissipate impact energy and thermal stress, which is key to achieving crack-free single-layer thick coatings.

[0117] Effect of stoichiometry on film quality (Comparative Example 2 and Comparative Example 4):

[0118] Comparative Example 4 showed insufficient curing agent, resulting in incomplete curing of the coating, with a salt spray resistance of only 720 hours and stickiness at high temperatures.

[0119] Analysis confirms the necessity of a 1:(0.8-1.2) mass ratio of components A and B. Only under the correct stoichiometric ratio can the epoxy groups in the resin and the active groups in the curing agent react fully to form a three-dimensional network structure with suitable crosslinking density, thereby ensuring the coating's resistance to media and thermal stability.

Claims

1. A single-layer flexible organosilicon-graphene composite anti-corrosion coating, characterized in that, It consists of component A and component B, wherein the mass mixing ratio of component A to component B is 1:(0.8-1.2); Component A comprises the following raw materials in parts by weight: 30-50 parts of flexible silicone resin; 5-15 parts of epoxy-based silane-modified graphene slurry; 2-5 parts of nano-silica; 3-8 parts of silicone toughening agent; Defoamer 0.2-1 part; Leveling agent 0.5-2 parts; Catalyst 0.1-0.5 parts; Component B comprises the following raw materials in parts by weight: 20-40 parts of polyurethane curing agent; Adhesion promoter 1-3 parts.

2. The single-layer flexible organosilicon-graphene composite anti-corrosion coating according to claim 1, characterized in that, The flexible organosilicon resin is an epoxy-terminated silicone oil modified resin; the organosilicon toughening agent is a polyether-modified silicone oil.

3. The single-layer flexible organosilicon-graphene composite anti-corrosion coating according to claim 1, characterized in that, The polyurethane curing agent contains ≥12% NCO groups by mass; the adhesion promoter is a silane coupling agent; and the nano-silica has a particle size of 10-50 nm.

4. The single-layer flexible organosilicon-graphene composite anti-corrosion coating according to claim 1, characterized in that, The catalyst is an organotin catalyst; the defoamer is a mineral oil defoamer; and the leveling agent is a polyether-modified organosilicon leveling agent.

5. The single-layer flexible organosilicon-graphene composite anti-corrosion coating according to claim 1, characterized in that, The epoxy-containing silane-modified graphene slurry is prepared by hydrothermal grafting and reduction of graphene oxide with an epoxy-containing silane coupling agent, followed by dispersion. The solid content of the epoxy-containing silane-modified graphene slurry is (5-15) wt%.

6. A method for preparing a single-layer flexible organosilicon-graphene composite anti-corrosion coating, characterized in that, The preparation of a single-layer flexible organosilicon-graphene composite anti-corrosion coating according to any one of claims 1-5 includes the following steps: S1. Preparation of epoxy-containing silane-modified graphene slurry: Graphene oxide and silane coupling agent are mixed in a solvent and subjected to hydrothermal reaction under closed high pressure. After the reaction is completed, the slurry is obtained by reduction, washing and redispersing. S2. Preparation of component A: Flexible organosilicon resin, nano-silica and organosilicon toughening agent are mixed and dispersed at high speed, then the epoxy-containing silane modified graphene slurry is added and dispersed at low speed, and finally leveling agent, defoamer and catalyst are added and stirred evenly. S3. Preparation of Component B: Mix and filter the polyurethane curing agent and adhesion promoter; S4. Mixing: Mix component A and component B in the specified proportions and allow them to mature before use.

7. The method for preparing a single-layer flexible organosilicon-graphene composite anti-corrosion coating according to claim 6, characterized in that, In step S1, the mass ratio of graphene oxide to silane coupling agent is 1:(0.3-0.7); the hydrothermal reaction temperature is 120-150℃, and the reaction time is 4-8 hours.

8. The method for preparing a single-layer flexible organosilicon-graphene composite anti-corrosion coating according to claim 7, characterized in that, In step S1, the silane coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane; the graphene oxide sheet diameter is ≤3μm.

9. The method for preparing a single-layer flexible organosilicon-graphene composite anti-corrosion coating according to claim 6, characterized in that, In step S2, the high-speed dispersion is performed at a rotation speed of 1000-1500 rpm for 15-25 minutes; the low-speed dispersion is performed at a rotation speed of 400-600 rpm for 20-40 minutes.

10. The method for preparing a single-layer flexible organosilicon-graphene composite anti-corrosion coating according to claim 6, characterized in that, It also includes the construction steps: applying the mixed and matured coating to the surface of the metal substrate, and controlling the dry film thickness of a single layer of coating to be 110-130μm.

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